US1677900A

US1677900A - Method of degasifying radiotubes

Info

Publication number: US1677900A
Application number: US28340A
Authority: US
Inventors: Frederick S Mccullough
Original assignee: Individual
Current assignee: Individual
Priority date: 1925-05-06
Filing date: 1925-05-06
Publication date: 1928-07-24
Anticipated expiration: 1945-07-24

Description

July 24, 1928. 1,677,900

F. S. M CULLOUGH METHOD OF DEGASIFYING RADIO TUBES Filed May 6, 1925 X? WNVENTOR.

A TTORNEY Y is energized, and this is continued until the PatentedJuly 24, 1928.

UNI-TED. STA'VTES PATENT OFFICE.

FREDERICK- s. MoGULIiOUGH, or wILKiNsBUne, PENNSYLVALATIA;

mnrnon or DEGASIFYING namoru'nns;

Application filed May 6. 1925 Serial No. 28,340.

heater. This cathode is generally coated to.

give high emission at relatively low temperatures. I v

In de-gasifying the usual type of-tube, in which the cathode is of the filament type, in which there is a materially smaller emitting surface than in the tube as above described having the full cylindrical cathode, the tube, after being connected on the pump and baked for the necessary period of time, has its cathode heated by the application of the filament voltage, after which a plate voltage is applied to the tube. With the plate voltage on, the oscillator is energized, that is, the radio frequency coil surrounding the tube in the pumping apparatus tube clears.

Such a process when applied to tubes of the cylindrical cathode type, where the size and capacity is so much greater than with the usual filament type cathode tube, the

late current arcsover upon the oscillator eing energized, dislntegratin and vaporizing or melting the high emlssion coating on the cathode and the cathode itself.

The object of the present invention is to provide a method of de-gasifying a tube of the cylindrical cathode type efliciently and withoutinjury to the cathode or the coating thereon.

In the drawing, I have illustrated a partially completed tube of the general type to which the present invention relates.

In the drawing, which is-in general a ver- I -tical section, 5 is the envelope of the tube having a base stem 6 in which is the sealing tube 7 that connects with the vacuum or exhausting line 8.- In the tube is a plate 9, a grid 10, and a cathode 11 carried on a heater element 12. A radio frequency coil'13 surrounds the tube when it is being pumped.-

This coil is in a suitable high frequency circuit. a

After being connected with the pump line for the desiredperiod during which the tube ma be baked, the baking is discontinued and a voltage is appliedto wires 12 leading to the heater, raising the temperature tubehavi'ng a low temperature of the heater and driving out the contained.

gases. 1 After the heater has been energized for a few seconds, until it has been brought to the glowing temperature, the external coil is energized, or, as expressed in the art, the oscillator is applied until the tube has cleared up and before any potential is put on the tube. By clearing up I mean that time when the glow inthe tube has practically vanished. Then the radio frequency current is shut down, and with the heater still in operation, the plate voltage is applied, and this is applied until the tube again clears up.

As the tube is quite highly evacuated before the plate voltage is applied, and as this is done after the oscillator is shut down,

the impedance of the tube when the plate voltage is applied is such that arcing between the plate. and cathode will not occur.

As it was heretofore considered necessary to apply the plate voltage While the oscillator was operating,'and as such operation with cylindrical cathode tubes frequently resulted in arcing, with injury to the cathode, it will be seen that the present .process is a distinct departure therefrom, and at the same time one which gives equallygood re--.

sults, so'far as driving out gas is concerned,

as does the former method and without dam- I age to the cathode.

In the drawing, A designates diagram- .matically the plate voltage circuit.

sheet metal cathodes which includes the steps of connecting the tube in a pumping sys-- tem, baking the tube, heating the cathode by energizing its heater from a source of a te rnatmg current, applying an oscillating field to the tube while thecathode remains heated, shutting off the oscillating field, alpplyin a plate voltage to the tube while t e catho e remains heated and after the oscillating field' has been shut down, and then sealing off the tube.

2. A method of de-gasifying an electron tubes having low temperature hig emission gh emission v latin oscillating field to the tube cylindrical cathode and a heater therefor which includes the steps of connecting the tube in a pumping system, baking the tube,

energizing the cathode heater, applying an while the cathode heater remains energized and until the tube clears, then shutting down the oscilfield and keeping the heater energize then applying a plate voltage until the tube again clears, andthen sealing off the tube,

3. A method of degasifying an electron tube having a gas absorbent cathodeheater and a sheet metal cathode supported on the 'ing the cathode heater to drive out absor heater which includes the steps of connecting the tube to a pumping system, energizd:

e gases, applying an oscillating field to the tube While the cathode heater-remains energized and until the heater has been substantially degasifie'd, then cuttin ofi. the oscillating field while keeping the eater energized, then applying a plate voltage until the tube clears, and sealing ofi the tube.

In testimony whereof I hereunto afiix my signature.

FREDERICK S. MCCULLOUGH.